1. Field of the Invention
The present invention relates to a print apparatus and a print control method using a continuous sheet.
2. Description of the Related Art
Japanese Patent Laid-Open NO. 2008-126530 discloses a print apparatus that performs a duplex printing on front and rear faces of a sheet in an inkjet system by using a lengthy continuous sheet wound into a roll. In this apparatus, while an image of a leading edge of the sheet fed from a sheet feeding unit is picked up, print positions for a plurality of subsequent images are set by using this positional information as a reference, and the sheet is cut by a cutter for each image after a print.
As the sheet used in the print apparatus is longer, an accumulation of sheet conveyance errors is larger. Also, in the print apparatus using liquid such as ink, the sheet length itself changes in some cases because of infiltration of moisture into the sheet, evaporation, or heat at the time of drying. As in Japanese Patent Laid-Open NO. 2008-126530, according to a method of picking up an image of a leading edge of the sheet first and using this as a reference for setting a subsequent print position, it is possible to obtain a high accuracy for the print position of the image in the vicinity of the leading edge. However, as being further away from the leading end, an influence of the conveyance error and sheet expansion and contraction is received, and the print displacement becomes larger as the sheet is longer.
In particular, when a plurality of images are disposed and printed sequentially on both faces of a continuous sheet, it is necessary to accurately match the print positions of the images on both the faces to each other, and relative errors of front and rear faces need to be smaller. However, a surface state of the sheet changed upon ink application. In a front face print and a rear face print, the sheet conveyance states are different from each other, and the relative errors tend to be increased. According to the system of Japanese Patent Laid-Open NO. 2008-126530, even when an alignment of the images on the front and rear sides in the vicinity of the leading edge attains a high accuracy, as being further away from the leading end, the influence of the conveyance error and sheet expansion and contraction is received, and an accuracy degradation in the alignment of the image on the front face and the image on the rear side of the sheet is expanded. In other words, as the sheet used in the one-time duplex printing is longer, the displacement of the image on the front face and the image on the rear side tends to be conspicuous.
The present invention has been made on the basis of a recognition of the above-mentioned problems. The present invention provides a print control method and a print apparatus with which when the duplex printing is performed on the continuous sheet, no matter how much the sheet used in the one-time duplex printing is longer, it is possible to suppress the print displacement of the images on the front face and the rear face.